In U.S. Pat. No. 3,598,402 (FIG. 7), a water sports apparatus is described, which is suited in particular for practicing such water sports as surfing, water skiing, etc.
In this water sports apparatus, the water is forced upwards over an inclined floor with a supercritical flow rate (a so-called torrential flow) that is greater than the fundamental wave velocity, so that the weight component of the athlete directed obliquely downward on the ski or board, modifiable by shifting of the center of mass, is at least partially commpensated for by the flow resistance in the opposite direction. In this way, without support, continuous practice of water sports is possible. By preference, the water flows in a cycle from a lower supply nozzle obliquely upward over the inclined floor surface, and is conducted back to the supply nozzle through a return duct placed below the container. A significant characteristic of this arrangement is that the high kinetic energy of the water on exiting from the supply nozzle is for the most part converted into potential energy, which, by virtue of the return duct, can be recovered. Thus for moving water in the cycle, only a small input of energy to the circulation pump is required, since it is only necessary to cover the flow losses.
However, there still arise difficulties in the starting process, since, if it is desired to avoid interruption of the water cycle in the circulation pump installed in the return duct, it is possible to begin with backflow of the water only when there is a sufficient flow of water over the upper edge of the floor surface, to the inlet to the return duct. On the other hand, however, the acceleration to the necessary flow rate of the water present in the return duct by the circulation pump requires a certain time, which is not available, because the flow upward along the floor surface is interrupted before the necessary flow rate is achieved.
A further water sports apparatus incorporating this principle is described by EP-A-96 216. As disclosed therein, with unchanged energy supply, an increased inclination angle of the floor surface is achieved, principally by means of the fact that water quantities slowed at the floor surface by friction, which would cause premature breakdown of the flow, are suctioned of or accelerated by supplying water with a higher flow rate. In one embodiment of this apparatus (FIG. 8 in EP-A-96 216) there is an elevated container, which holds the quantity of water required for starting, at the side of the upper edge of the floor surface, whereby during starting the water passes from the elevated container through the return duct to the supply nozzle. Here, the circulation pump is actually placed in front of the opening of the supply nozzle, so that the difficulties of starting are reduced, however, hear again, several disadvantages arise, which complicate an attractive implementation in practice.
In familiar water sports devices, along the upper edge of the inclined floor surface, extends the grate covering the inlet to the return duct, which is required for safety reasons. This grate prevents fallen athletes and their equipment (surfboards, water skis, etc.) from being sucked into the return duct. It has been seen, however, that the exiting of fallen athletes in the area of the grate, and especially the removal of water sports equipment, is relatively difficult, so that generally external assistance is required. In addition, there is the danger that in the process, the water circulation will be so disturbed that the supercritical torrential flow on the rising floor surface will be interrupted. However, for restarting, it is necessary after closing the supply nozzle to return the water on the inclined floor surface to the elevated container.
A further disadvantage of water sports devices of this type is the fact that they are suitable exclusively for the type of sports described, and thus are to be erected independently of existing or newly-built swimming pools, for example in recreation centers.
The invention has undertaken the task of refining a water sports apparatus of the type cited, in such a way that not only trouble-free starting and operation are possible, but also the exiting of the athlete, especially after a fall, and the removal of sport equipment without difficulty. Furthermore, it is intended that a possibility be found to configure the water sports apparatus as an integral component of a large swimming pool system in a recreation center.